It is very important to supply semiconductor devices, such as a bipolar or field effect transistor with excellent performances at low basic prices. Particularly, basic circuit elements mentioned in the above play the most important roles in a complicated semiconductor circuit, such as a semiconductor integrated circuit, and then the improvements of the methods for fabricating the bipolar and field effect transistors are one of the most important subjects in the field of the semiconductor device industry.
From the view point of the basic prices of the bipolar and field effect transistors, it is undesirable that the number of steps involved in the fabricating process of these transistors increases. From the view point of the performance of the devices, undesirable capacitors between the electrodes should be as small as possible.
In the semiconductor integrated circuit, the bipolar and field effect transistors are used on the same chip in most cases. Then, in fabricating such a semiconductor integrated circuit, it is desirable that some steps in fabricating the bipolar and field effect transistors can be progressed simultaneously, to decrease the steps of fabricating the semiconductor integrated circuit.